Convertible Debt and Notes Payable - Convertible Debt (Details) - USD ($)		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 14, 2017
Debt and Capital Lease Obligations [Line Items]
Purchase of treasury stock, cost		$ 47,300,000
Convertible debt	[1]	80,808,000	$ 118,688,000
Amortization of debt discount (premium)		4,490,000	4,598,000	$ 5,473,000
Gain/(loss) on debt extinguishment		2,719,000	0	(556,000)
Embedded Derivative, No Longer Bifurcated, Amount Reclassified to Stockholders' Equity				28,974,000
Convertible Debt
Debt and Capital Lease Obligations [Line Items]
Convertible debt		80,808,000
Convertible debt, unamortized discount		6,700,000	14,900,000
2022 convertible note | Convertible Debt
Debt and Capital Lease Obligations [Line Items]
Debt Instrument, Face Amount					$ 135,000,000.0
Debt Instrument, Convertible, Conversion Price					$ 17.375
Convertible debt		88,100,000
Interest on Convertible Debt, Net of Tax		4,000,000.0	4,100,000	4,100,000
Convertible debt, unamortized discount					$ 23,400,000
Amortization of debt discount (premium)		4,600,000	$ 4,300,000	$ 4,000,000.0
Debt Instrument, Interest Rate, Effective Percentage					7.13%
Debt Issuance Costs, Gross					$ 2,200,000
Extinguishment of Debt, Amount		70,500,000
Gain/(loss) on debt extinguishment		2,700,000
Debt Instrument, Repurchased Face Amount		46,900,000
Embedded Derivative, No Longer Bifurcated, Amount Reclassified to Stockholders' Equity		29,600,000
Write off of Deferred Debt Issuance Cost		400,000
Write off of pro rate unamortized discount while extinguishing debt		$ 3,600,000

[1] The carrying amount of the convertible debt includes an unamortized discount of $6.7 million and $14.9 million as of December 31, 2020 and 2019, respectively.